Mast fairing for a sailboat

ABSTRACT

A mast fairing for a sailboat includes an upper fairing and an optional lower fairing configured to reduce turbulent airflow over the upwind and downwind sides of a sail. The upper fairing includes a fairing wrap includes a central segment configured to wrap around a mast, a left-side panel, a right-side panel, and a sail track attached to trailing edges of the left- and right-side panels. One or more fairing supports are optionally attached to the sail track between the left- and right-side panels of the fairing wrap. The optional lower fairing includes a central segment, a left-side panel, and a right-side panel configured for installation on a mast and boom below the upper fairing. The upper and lower fairings reduce turbulent airflow over the surfaces of a sail and increase regions of laminar airflow to improve the performance of the sail.

FIELD OF THE INVENTION

Embodiments are related generally to equipment for improving aerodynamic lift generated by wind flowing over a sailboat sail and more particularly to equipment for increasing a size of a region of laminar air flow and reducing a size of a region of turbulent air flow over sailboat sails.

BACKGROUND

A sailboat sail made from a pliable material such as sailcloth, thin polymer sheet, and/or composite materials assumes a curved surface shape under the influence of wind striking the sail. Air flowing in smooth layers over the upwind and downwind sides of the curved sail generates aerodynamic lift, a force which may be used to propel a sailboat in a forward direction of travel. As wind velocity increases, aerodynamic lift increases until airflow over the curved sail transitions from smooth flow with air molecules moving parallel to sail surfaces, also referred to as laminar flow, to turbulent flow, a chaotic flow condition with air molecules moving in many directions. Turbulent airflow at or near the surfaces of the sail reduces the component of aerodynamic lift available to propel the sailboat forward and increases mechanical stresses acting on the mast, rigging, and sails.

Laminar and turbulent flow may be detected by placing telltales at different locations on a sail, by making air pressure measurements at different locations on a sail, by making air velocity measurements at different locations on a sail, and by other means. Such measurements show that turbulent flow and laminar flow are influenced by wind velocity, the radius of curvature of the sail (the “flatness” of the sail), the location of the deepest part of the curvature relative to the leading edge of the sail, by obstructions to airflow near the sail, and by other factors.

The mast and other parts of the rigging used to hold up a sail and control the shape of the sail contribute to turbulent flow over the sail. A widely-used sailing rig couples the leading edge of a sail (the “luff”) to the aft side of a mast. The bottom edge of the sail (the “foot”) is held along one or more spars (on some boats, the “boom”) extending aft from the mast. A hinge structure (on some boats, the “gooseneck”) rotatably couples the boom to the mast, although other arrangements are known. When a boat sails upwind, that is, with the apparent wind at an angle less than ninety degrees to the boat's direction of travel, air flowing around the mast creates a turbulent flow region along the luff of the sail. The turbulent flow region may be largest on the downwind side of the sail, sometimes extending from the luff to about one-fifth to one-third of the sail's chord length.

Laminar flow capable of generating aerodynamic lift for propelling the sailboat is limited to the part of the sail between the turbulent flow region and the trailing edge of the sail (the “leach”). Air flowing downward from the foot of the sail toward the boat hull, rather than along the full chord length of the sail, further reduces aerodynamic lift for propelling the sailboat.

SUMMARY

An example apparatus embodiment of a mast fairing includes an upper fairing and a lower fairing. The upper fairing includes a fairing wrap. An example fairing wrap includes a central segment sufficiently pliable to conform to a curved surface of a sailboat mast; a left-side panel joined to the central segment, with the left-side panel including a left-side trailing edge; a right-side panel joined to the central segment opposite the left-side panel, with the right-side panel including a right-side trailing edge; and a sail track positioned between the left-side trailing edge and right-side trailing edge. The sail track is configured for coupling to a sail luff. The lower fairing includes a lower fairing central segment sufficiently pliable to conform to the curved surface of the sailboat mast; a left-side lower fairing panel joined to the lower fairing central segment; and a right-side lower-fairing panel joined to the lower fairing central segment opposite the left-side lower fairing panel.

The left-side panel and/or the right-side panel of the upper fairing may optionally be formed separately from the central segment and attached strongly to the central segment, or may optionally be integrally formed with the central segment. The left-side panel and the right-side panel may each be optionally be formed with a slot positioned to receive a mast spreader. A slot may optionally extend onto the central segment of the upper fairing. Additional slots may optionally be provided to enable the upper fairing to move past other mast attachments such as an attachment point for a forestay, brackets for lights or antennas, and the like.

In some embodiments, the upper fairing may optionally be formed with an overall length dimension corresponding to at least 70% (seventy percent) of a separation distance from a gooseneck for a boom to a top end of the sailboat mast.

An upper fairing may optionally include a fairing support attached to the sail track. The optional fairing support may be positioned between the sail track and the central segment of the fairing wrap. The upper fairing optionally includes more than one, and optionally many, of the fairing support. An example fairing support optionally includes a front wall formed with a flat surface on a side facing the mast or alternatively with a radius of curvature greater than or equal to a radius of curvature of the curved surface of the sailboat mast; a first side plate coupled to a left side of the front wall; and a second side plated coupled to a right side of the front wall opposite the first side plate. When connected to the fairing wrap, the left-side trailing edge attaches to the first side plate and the right-side trailing edge attaches to the second side plate.

The left-side lower fairing panel may be formed with a length dimension corresponding to at least 50% of a separation distance from a front side of the sailboat mast to a clew of the sail. The right-side lower fairing panel may be formed with the same length dimension of the left-side lower fairing panel. The left-side lower fairing panel and the right-side lower fairing panel are optionally integrally formed as separate pieces strongly attached to the lower fairing central segment, or may optionally be integrally formed with the lower fairing central segment.

Another example apparatus embodiment includes a fairing configured for sliding contact with a sailboat mast. The example fairing includes a fairing wrap, a fairing support, and a sail track attached to the fairing support. The fairing includes a fairing wrap having a central segment sufficiently pliable to conform to a curved surface of a sailboat mast; a left-side panel joined to the central segment, with the left-side panel having a left-side trailing edge; and a right-side panel joined to the central segment opposite the left-side panel, with the right-side panel having a right-side trailing edge. The fairing support is preferably positioned between the central segment, the left-side trailing edge, and the right-side trailing edge, with an example fairing support including a front wall; a first side plate coupled to a left side of the front wall; and a second side plated coupled to a right side of the front wall opposite said first side plate. The front wall of the fairing support may be flat or may alternatively be formed with a radius of curvature corresponding to a radius of curvature of the curved surface of the sailboat mast.

The sail track may optionally be attached to the first side plate of the fairing support. Alternatively, the sail track may optionally be attached to the front wall of the fairing support.

Some embodiments of the fairing optionally include a second of the fairing support positioned between the central segment, the left-side trailing edge, and the right-side trailing edge; a first fairing plate attached to the first side plate of the fairing support and the first side plate of the second fairing support; and a second fairing plate attached to the second side plate of the fairing support and the second side plate of the second fairing support.

The sail track may optionally be configured to carry one, and optionally many, sail cars configured to be coupled to a sail luff. Alternatively, the sail track may optionally be configured to receive a bolt rope on a sail luff.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view toward a left side of an example embodiment of a mast fairing having an upper fairing and a lower fairing installed on an example sailboat.

FIG. 2 is a view toward a left side of an example embodiment of the upper fairing.

FIG. 3 is a view toward a left side of an example embodiment of the upper faring having a tapered width, narrower at the top end than the bottom end.

FIG. 4 is a cross-sectional view A-A showing an example of the upper fairing positioned around an example of a sailboat mast, with the upper fairing and sail in an example of a position for sailing a boat on a port tack, and the viewing direction from the top of the mast toward the sailboat hull, and further illustrating an example of an upper fairing 102 that omits the optional fairing supports used in some other embodiments.

FIG. 5 continues the example of FIG. 4, showing the same example upper fairing and mast in an example of a position for sailing a boat on a starboard tack.

FIG. 6 is an example of a turbulent flow region on the downwind side of a mast along the luff of a sail for a sailboat using a sailing rig previously known in the art (PRIOR ART).

FIG. 7 shows a view toward an end of an example of a fairing support used in some embodiments of an upper fairing, further illustrating examples of a fairing support with a flat front wall and an alternative optional configuration with a radiused front wall.

FIG. 8 shows a view into an open side of the example fairing support of FIG. 7.

FIG. 9 shows an alternative cross-sectional view A-A with an example upper fairing having the optional fairing support of FIGS. 7-8.

FIG. 10 is a view toward a left side of an example sailboat equipped with an alternative embodiment of a mast fairing including fairing plates attached along the trailing edges of the fairing wrap for the upper fairing, and further including the lower fairing example of FIG. 1.

FIG. 11 shows cross-sectional view B-B with an example upper fairing having a fairing support configured for attachment of the fairing plates of FIG. 10, a sail track attached to the front wall of the fairing support, and the sail track configured to accept a bolt rope along the luff of an example sail.

FIG. 12 shows an alternative cross-sectional view B-B with an example upper fairing having a fairing support configured for attachment of the fairing plates of FIG. 10, a sail track attached to the front wall of the fairing support, and a sail track configured to accept sail cars coupled by toggles to brackets along the luff of an example sail, and further illustrating an example of a fairing support displaced away from the surface of the mast with an intervening gap between the fairing support and the mast.

FIG. 13 is a front view of an example tack bridle for allowing the sail tack to displace laterally relative to the boom as the mast fairing rotates.

FIG. 14 is a view toward a left side of the example lower fairing of FIG. 1 and FIG. 10.

FIG. 15 is a view toward a top edge of the example lower fairing of FIG. 15, showing an example of a mast cross-section at the front of the lower fairing.

FIG. 16 is a partial enlarged view of the lower fairing, boom, and sail of FIG. 7, illustrating an example of control lines and other hardware for adjusting the position of the lower fairing tack along the boom, and further illustrating an example of the upper edge of the lower fairing extending above the foot of the sail.

FIG. 17 is an alternative cross-sectional view B-B showing a simplified representation of an example roller furler for a sail attached to an example fairing support.

DESCRIPTION

Example apparatus embodiments of a mast fairing slidably engage with a mast on a sailboat to increase aerodynamic lift from a sail by increasing laminar flow over the sail and reducing an area of turbulent flow along the luff of the sail. The mast fairing rotates about the mast in response to changing wind conditions, sailboat pointing direction, and changes in sail trim, with the luff of the sail engaged with a sail track attached to the mast fairing rather than a sail track in or on the mast. The example mast fairing includes an upper fairing configured to be installed on the mast above the gooseneck for the boom and an optional lower fairing configured to be installed on the mast below the upper fairing and extending along the boom, preferably to the clew of the sail, and preferably with a top edge of the lower fairing extending above the foot of the sail.

Embodiments of the mast fairing are effective for reducing loss of aerodynamic lift from turbulent flow induced by wind flowing around the mast onto the upwind and downwind sides of a sail. For sailboats not equipped with one of the disclosed mast fairing embodiments, turbulent flow developing along the luff of a sail is known to reduce the aerodynamic lift from the sail by at least 35 percent. An additional 25 percent of the lift theoretically available from a sail can be lost when air passes under the boom instead of over a sail surface. The disclosed embodiments are effective for preventing and/or recapturing a substantial fraction of these losses. Improvements of aerodynamic lift from the disclosed embodiments are so substantial that a mast fairing embodiment added to a previously built sailboat enables the sailboat to be sailed as efficiently without a headsail as a boat with a headsail that has not been equipped with the mast fairing embodiment, where efficiency may be defined as a ratio of boat speed to wind speed. For a new sailboat constructed with a mast fairing embodiment as part of the original equipment, the mast and sail may be made smaller and/or standing and running rigging made lighter to achieve aerodynamic lift and sailing efficiency comparable to other boats with taller masts and/or larger sails but lacking a mast fairing.

For the discussion to follow, directions are given with respect t to directions commonly used for a boat in the water. The port side refers to the left side when facing toward the bow of a boat from the stern. The front side of a part of an embodiment is the side closest to the bow of the boat when the mast fairing is installed on a mast. The back side of an embodiment is the side closest to the stern of the boat when the mast fairing is installed on a mast. References to the upwind side and downwind side of the sail and/or mast are made with respect to the apparent wind direction, where the apparent wind is the vector sum of the boat velocity and the velocity of the true wind.

The disclosed embodiments of a mast fairing are most effective on sailboats with stayed masts and/or a sail coupled to a sail track and raised and lowered by a halyard. The illustrated examples of a sailboat show a mast with a boom attached by a gooseneck and spreaders attached to the mast. Some standing rigging has been omitted in the figures to avoid visual clutter, but it will be appreciated that the disclosed embodiments are effective on sailboats whether or not the sailboat uses spreaders, a forestay, and/or a backstay. Furthermore, although the examples to follow use a mainsail as an example of a sailboat sail, the embodiments are effective for other types of sails. For example, embodiments are effective for improving laminar flow over a mizzen set on a mizzenmast.

Turning now to the example embodiments of a mast fairing in the figures, FIG. 1 shows an example of a sailboat 1000 equipped with an example embodiment of a mast fairing 100 including an upper fairing 102 and a lower fairing 104. FIGS. 2-3 show some additional details of examples of the upper fairing 102. The view in FIG. 1 is toward the port side 1018 of a sailboat hull 1004 having its bow 1014 at the left side of the figure and the stern 1016 at the right side of the figure. An example forestay 1010 extends from the bow 1014 to a front side of the mast 1002. In the example of FIG. 1, two spreaders 1070 extend outward toward the viewer from the left side of the mast 1002. Two more spreaders extending out from the right side of the mast are not visible in the figure. At least one shroud 1082 may be present to stabilize the mast 1002. When installed, an example backstay 1012 extends from the stern 1016 to the back side of the mast, possibly to a masthead cap or masting casting 1022. A mainsheet 1042 provides position control of the boom 1006. An optional yang 1040 coupled to the mast 1002 and the boom 1006 applies a controllable downward force against the sail 1024. An example sail 1024 has a leading edge or lull 1032 slidably engaged with the upper fairing 102, a trailing edge or leech 1034 joined to the luff at the head 1026, and a foot 1036 opposite the head 1026. The sail tack 1028 is near the luff 1032 and the foot 1036 and the sail clew 1030 is near the leech 1034 and the foot 1036. An eyelet 1038 near the head 1026 provides an attachment point for the halyard 128. The sail optionally includes an eyelet or other fitting 1078 for attachment of a Cunningham downhaul. The example sail 1024 optionally includes one or more sail battens 1046. The sail battens 1046 optionally extend all the way from the leech 1034 to the tack 1032 of the sail 1024.

The upper fairing has an overall length 178 (ref. FIG. 2) that preferably extends at least 70% of a distance 1076 from a gooseneck 1008 joining the boom 1006 and the mast 1002 up to the masthead cap 1022 at the top of the mast 1020. The upper fairing is most effective for reducing turbulent flow and improving laminar flow over the sail when the upper fairing has a length 178 approximately equal to the length of the sail luff. The upper fairing 102 includes a fairing wrap 106 configured to be wrapped around a front side of the mast 1002 and extending toward the stern 1016 past the back side of the mast. The fairing wrap 106 includes a central segment 168 that conforms to a radius of curvature 1072 of the front side of the mast (ref. FIGS. 4-5 for examples), a left-side panel 170 attached to the central segment 168, and a right-side panel 172 (not visible in FIG. 1) also attached to the central segment 168. The left-side panel 170 and right-side panel 172 may be formed separately from the central segment 168 and strongly joined to the central segment, or may alternatively be integrally formed with the central segment. In some embodiments, a sail track 110 joins to the left-side panel 170 along a left-side trailing edge 174 and to the right-side panel 172 along a right-side trailing edge 176. As will be seen in later figures, in some embodiments the sail track is attached to a fairing support 108 rather than the trailing edges of the fairing wrap.

When a sail is present, the luff 1032 of the sail couples to the sail track 110 in the upper fairing 102 rather than a sail track attached to or formed as an integral part of the mast 1002. When the upper fairing 102 rotates about the mast 1002 in response to changes in wind direction or sailing direction, the sail track 110 and the head 1026, luff 1032, and tack 1028 of the sail 1024 preferably move with the upper fairing. The upper fairing 102 is prevented from slipping down the mast, for example when the sail is being lowered, by a fairing line 124 connected to the mast or mast cap and is prevented from being pulled up the mast, for example when raising the sail, by another fairing line attached to the mast and passing through a grommet 126 near the lower end of the upper fairing.

For a mast having spreaders or other projections, the upper fairing 102 may be formed with slots 152 through the central segment 168 and parts of the left-side panel 170 and right-side panel 172. The slots 152 enable the upper fairing 102 to rotate about the mast 1002 without the spreaders or other hardware projecting from the mast interfering with the rotation.

In the example upper fairing 102 of FIG. 1 and FIG. 2, the width 154 at the top of the upper fairing 102 is approximately equal to the width 156 at the bottom of the upper fairing. Alternatively, the upper fairing may be formed with a tapering width increasing from top toward the bottom, with the width 154 at the top of the upper fairing 102 less than the width 156 at the bottom of the upper fairing, as suggested in the example of FIG. 3. For example, the widths (154, 156) in FIG. 2 may differ from one another by less than about one inch (2.5 centimeters), while the widths (154, 156) in FIG. 3 may differ from one another by a substantial amount, for example at least six inches (15 centimeters).

FIGS. 4 and 5 show examples of an embodiment 100 of the upper fairing 102 positioned to provide laminar flow around a mast and onto a sail and reduce turbulent flow along the luff of the sail. FIG. 4 and FIG. 5 further illustrate an example embodiment of an upper fairing 102 with the fairing wrap 106 having a central segment 168 joined to a right-side panel 172 and a left-side panel 170. The central segment is preferably sufficiently pliable to readily conform to the radius 1072 of the outer surface 1054 of the mast 1002. A sail track 110 joins to the right-side panel along the right-side trailing edge 176 and to the left-side panel along the left-side trailing edge 174. An optional bolt rope attached to the right-side trailing edge 176 may engage a corresponding channel formed in the sail track 110. The left-side trailing edge 174 may be attached to the sail track by a fastener 122. Alternatively, either one or both trailing edges of the fairing wrap 106 may attach to the sail track 110 by a bolt rope or by fasteners. Examples of a fastener 122 include, but are not limited to, a bolt, a screw, a rivet, adhesive, a fused area, and stitching.

The example sail track 110 may be formed with a slot or channel 118 shaped to accept a bolt rope along the luff of a sail 1024. As will be seen in later figures, the sail track may alternatively be configured to accept sail cars. FIGS. 4-5 further illustrate an example of a mast formed with a slot 1050 for a bolt rope along the back side of the mast. The mast slot 1050, when present, is not used for attachment of a sail when the mast fairing 100 is in place on the mast.

An example of a direction of boat travel is marked by an arrow 1060 in FIGS. 4 and 5. An example of a relative wind direction is marked by an arrow 1062. The sail 1024 is curved by the wind 1062 with the sail convex on the upwind side 1056. The upper fairing is preferably free to rotate about the mast from a port broad reach to a starboard broad reach, with the fairing wrap 106 and sail 1024 smoothing airflow around the mast to provide laminar flow 1066 around the mast and across the upwind 1056 and downwind 1058 sides of the sail and reducing or eliminating the size of the region of turbulent flow along the sail luff. FIG. 4 shows an example of the fairing wrap 106, sail track 110, and sail 1024 positioned for sailing on a port tack (wind coming over the port side 1018 of the sailboat 1000). FIG. 5 shows the same embodiment 100 as FIG. 4, but rotated into position for sailing on a starboard tack. In the examples of FIGS. 4 and 5, laminar flow 1066 around the mast and along the luff on both sides of the sail is established and maintained on both tacks and regions of turbulent flow along the luff are reduced in size or eliminated, compared to a mast and sails without a mast fairing.

In contrast to the laminar flow 1066 established by mast fairing embodiments 100, FIG. 6 shows an example of a region of turbulent flow 1064 resulting from an apparent wind 1062 flowing past a mast 1002 for a boat not equipped with an embodiment 100, with the boat traveling in the direction 1060. The region of turbulent flow, represented in the figure by a pattern of vortex symbols along the sail luff on the downwind side of the sail, is in reality more chaotic than suggested by the regularity of the symbols in the figure. The region of turbulent flow 1064 reduces the area of the sail subjected to laminar flow and reduces the aerodynamic lift from the sail, under some conditions by at least 20%.

As suggested in the examples of FIGS. 1, 2, 3, and elsewhere in the figures, some mast fairing embodiments 100 include an upper fairing 102 having fairing supports 108 positioned to move the sail track 110 and parts of the fairing wrap 106 away from the mast to provide laminar flow around a protected space between the mast and the sail luff. A furling system and/or other equipment attached to the mast may be placed in the protected space without the equipment causing turbulent flow over the sail. The fairing supports are not held firmly to the mast and may move away from the mast for some installations and some sailing conditions without causing problems for the sail track and other parts of the upper fairing. The example fairing support 108 of FIGS. 7-8 includes a front wall 130 with an approximately flat exterior surface. Two support plates 132 are joined to the front wall 130. Each support plate 132 optionally includes one or more apertures 136 for receiving fasteners 122 to attach a sail track and/or fairing wrap 106. As suggested by the phantom lines in FIG. 7, the front wall 130 may alternatively be formed with a radius of curvature 134 greater than or equal to a corresponding exterior radius of curvature 1072 on a surface of a mast. The front wall 130 may have a layer of slippery material affixed or a layer of slippery material may be applied to the mast in the vicinity of the contact area for the fairing support, although some mast surfaces will not need such slippery material for good response of the mast fairing to changes in wind conditions, for example because the fairing supports may not be in contact with the mast during some sailing conditions.

An example of the fairing support 108 of FIGS. 7-8 is shown in alternative section A-A in FIG. 9. When installed in an upper fairing, the optional fairing supports are interposed between the aft exterior surface of the mast 1002, the left-side panel 170 and right-side panel 172 of the fairing wrap 106, and the sail track 110. In the example of FIG. 9, the fairing support 108 and the left-side panel 170 and right-side panel 172 attach to flanges 138 extending forward toward the mast from the sail track 110. Alternately, the left-side panel 170 and right-side panel 172 attach directly to the support plates 132 of the fairing support 108.

FIG. 9 shows an example of a mast 1002 omitting an internal sail track and an external sail track attached to an outer surface of the mast. FIG. 9 further illustrates an example of an embodiment 100 including a sail track 110 formed with a channel 118 configured to accept sail cars 140. Each sail car includes a toggle engaging a corresponding toggle bracket 142 bolted or riveted to the luff of the sail 1024.

A fairing support 108 may optionally be configured to hold fairing plates 116 positioned to cover a gap that may exist between the mast and the luff of the sail. As suggested in the example of FIG. 10, each fairing plate 116 is attached to at least one, and generally at least two, fairing supports 108. The optional fairing plates 116 provide for smooth laminar flow between the fairing wrap and sail for embodiments 100 having the sail track attached to the front wall of the fairing support, as suggested in the examples of a mast fairing 100 in FIGS. 10-12.

Another advantage of a mast fairing 100 including fairing plates is the space provided between the mast and fairing plates for sail furling equipment along the mast, for example an external mainsail roller furling system. Roller furling provides a safe and convenient way to reduce sail area, but the rolled portion of a partially-furled sail is known to substantially increase turbulent flow along the sail luff, decrease laminar flow, and therefore decrease sailing efficiency. When external roller furling is installed on the mast, the furling drum and possibly other parts of the furling system may be attached to fairing supports 108, thereby enabling the furling system and the furled portion of the sail to rotate around the mast with movement of the upper fairing 102. The fairing plates 116 cover the furling drum and the partially furled sail, improving laminar flow around the mast and onto the unfurled part of the sail, substantially improving sailing performance with a furled sail compared to a boat without a mast fairing 100. The fairing plates 116 closest to the gooseneck 1008 may optionally be cut away as at 184 to make room for a flaked mainsail or a mainsail rolled around the boom. An example of a simplified representation of a roller furler 1086 for a sail is shown in FIG. 17, with the roller furler attached to a fairing support 108 to enable the roller furler to rotate with the upper fairing 106.

FIG. 11 shows cross-sectional view B-B of an example fairing support 108 having a sail track 110 attached to the front wall 130 of the fairing support. In the example of FIG. 11, the sail track 110 is configured to accept a bolt rope 1052 attached to the luff of the sail 1024. The bolt rope 1052 slidably engages a channel 118 formed in the sail track. Sail slugs or sail slides 1048 may optionally replace the bolt rope 1052.

FIG. 12 replaces the sail track configured for a bolt rope or sail slides of FIG. 11 with a sail track 110 configured to accept sail cars 120. For the examples of FIGS. 11 and 12, the right-side panel 172 and a first fairing plate 116 are both attached to a first support plate 132, and the left-side panel 170 and a second fairing plate 116 are attached to the second support plate 132 of the fairing support 108. As in FIG. 11, the embodiment of FIG. 12 has the right-side panel 172 of the fairing wrap 106 and a first fairing plate 116 attached to a first support plate 132 of the fairing support 108 and the left-side panel 170 and a second fairing plate 116 attached to a second support plate 132. FIG. 12 further illustrates that the fairing spacer 108 may become displaced away from the mast by a gap 196 under some sailing conditions and the upper fairing 102 will continue to function properly, for example by rotating freely around the mast with changes in the direction of the apparent wind. For some optional installations, the size of the gap 196 may be selected to allow the fairing spacer 108 to rotate around the mast without damaging an external sail track affixed to the back side of the mast. An external sail track attached to the mast, if present, is not used by the mast fairing 100, and may be removed from the mast when an embodiment 100 is to be installed.

For some installations of a mast fairing 100 it may be advantageous to provide a tack bridle 114 that enables the sail tack to displace laterally with rotation of the mast fairing 100 to avoid twisting the sail. An example of a tack bridle 114 configured for sliding connection of a downhaul to the sail tack is shown in the example of FIG. 13. A transverse rod 164 passes through the tack eyelet of the sail. Bridle lines 158 with a fixed attachment 162 to a bridle control line 194 attach with shackles 160, rings, or the like to opposite ends of the transverse rod 164, passing around the boom with the fixed attachment 162 below the boom and the bridle control line 194 led aft to the cockpit through turning blocks on the mast and deck (not illustrated). The tack of the sail is free to slide along the transverse rod 164 as the upper fairing 102 rotates about the mast, preventing sail twist along the foot and luff near the tack.

FIGS. 14-15 show some features of an example lower fairing 104. The example lower fairing 104 includes a lower fairing central segment 190 configured to wrap around a front side of the mast 1002. A lower fairing left-side panel 186 and a lower fairing right-side panel 188 are joined to, or alternately formed as an integral part of, the lower fairing central segment 190. A lower fairing length dimension 182 from the front of the mast to the back edges of the lower fairing right- and left-side panels is preferably at least as long as a separation distance between the tack and clew of the sail. A lower fairing clew 180 is provided on each of the lower fairing right- and left-side panels to engage with a lower fairing outhaul 148 coupled to the boom, as shown for example in FIG. 1, FIG. 10, and FIG. 16. The aft end 144 may be angled to provide clearance around a sailboat cabin, dodger, winches, or other structures within the area swept by movements of the lower fairing. The side panels of the lower fairing may optionally include windows 146 made from a transparent material to facilitate visibility through the lower fairing. The side panels of the lower fairing may further optionally include a vertical batten 150 affixed to the lower channel side panel or alternatively held in a batten pocket. The upper ends of the battens are preferably displaced away from the top edges 192 of the lower fairing 104 to enable the top edges 192 to extend smoothly upwards past the foot of the sail and/or around the sides of the boom.

FIG. 16 shows a partial enlarged view of parts of an example lower fairing 104, boom 1106, and sail. A sail outhaul 1084 passes through an eyelet at the clew 1030 of the sail and around a pulley in the boom (not visible), with the sail outhaul optionally led through the boom to the mast and aft to the cockpit in the conventional manner. In the example embodiment 100 of FIG. 1, the upper edge 192 of the lower fairing 104 does not extend as high as the foot of the sail 1036. FIG. 16 illustrates an optional alternative configuration in which the upper edge 192 of the lower fairing extends over the foot of the sail. In another alternative embodiment, the upper edges 192 of the lower fairing reach up to the bottom of the boom without extending up the sides of the boom. The lower fairing 104 extends along the boom with the upper edge 192 of the lower faring below the foot of the sail 1036 in the example. A lower fairing outhaul 148 passes through the clew 180 of the lower fairing 104 and around an outhaul block 198 suspended from the sail outhaul 1084, providing for adjustment of the main clew and lower fairing clew positions with a single line. The lower fairing outhaul 148 joins to a control line 200 led to the mast and back to the cockpit. The control line 200 is preferably elastic to hold the lower fairing in tension while sailing. The lower fairing may be depowered rapidly by slacking the control line 200.

Unless expressly stated otherwise herein, ordinary terms have their corresponding ordinary meanings within the respective contexts of their presentations, and ordinary terms of art have their corresponding regular meanings. 

What is claimed is:
 1. An apparatus, comprising: an upper fairing, comprising: a fairing wrap, comprising: a central segment sufficiently pliable to conform to a curved surface of a sailboat mast; a left-side panel joined to said central segment, said left-side panel comprising a left-side trailing edge; a right-side panel joined to said central segment opposite said left-side panel, said right-side panel comprising a right-side trailing edge; and a sail track positioned between said left-side trailing edge and said right-side trailing edge, said sail track configured for coupling to a sail luff; and a lower fairing, comprising: a lower fairing central segment sufficiently pliable to conform to the curved surface of the sailboat mast; a left-side lower fairing panel joined to said lower fairing central segment; and a right-side lower-fairing panel joined to said lower fairing central segment opposite said left-side lower fairing panel.
 2. The apparatus of claim 1, wherein said left-side panel is integrally formed with said central segment, and said left-side panel is formed with a slot positioned to receive a mast spreader.
 3. The apparatus of claim 1, wherein said right-side panel is integrally formed with said central segment, and said right-side panel is formed with a slot positioned to receive a mast spreader.
 4. The apparatus of claim 1, wherein said upper fairing is formed with an overall length dimension corresponding to at least 70 percent of a separation distance from a gooseneck for a boom to a top end of the sailboat mast.
 5. The apparatus of claim 1, further comprising a fairing support attached to said sail track.
 6. The apparatus of claim 5, wherein said fairing support is positioned between said sail track and said central segment of said fairing wrap.
 7. The apparatus of claim 5, further comprising an additional plurality of said fairing support attached to said sail track.
 8. The apparatus of claim 5, wherein said fairing support comprises: a front wall; a first side plate coupled to a left side of said front wall; and a second side plated coupled to a right side of said front wall opposite said first side plate, wherein said left-side trailing edge attaches to said first side plate and said right-side trailing edge attaches to said second side plate.
 9. The apparatus of claim 8, wherein said front wall is formed with a radius of curvature greater than or equal to a radius of curvature of the curved surface of the sailboat mast.
 10. The apparatus of claim 1, wherein said left-side lower fairing panel comprises a length dimension corresponding to a separation distance from a front side of the sailboat mast to a clew of a sail coupled to the sailboat mast.
 11. The apparatus of claim 10, wherein said right-side lower fairing panel comprises said length dimension of said left-side lower fairing panel.
 12. The apparatus of claim 1, wherein said left-side lower fairing panel and said right-side lower fairing panel are integrally formed with said lower fairing central segment.
 13. The apparatus of claim 1, further comprising a control line and an outhaul block, said control line passing through a tack of said lower fairing and through said control block, with said control block configured to be suspended from a sail outhaul line.
 14. A fairing configured for sliding contact with a sailboat mast, said fairing comprising: a fairing wrap, comprising: a central segment sufficiently pliable to conform to a curved surface of a sailboat mast; a left-side panel joined to said central segment, said left-side panel comprising a left-side trailing edge; a right-side panel joined to said central segment opposite said left-side panel, said right-side panel comprising a right-side trailing edge; and a fairing support positioned between said central segment, said left-side trailing edge, and said right-side trailing edge, said fairing support comprising: a front wall; a first side plate coupled to a left side of said front wall; and a second side plated coupled to a right side of said front wall opposite said first side plate; and a sail track attached to said fairing support.
 15. The fairing of claim 14, wherein said sail track is attached to said first side plate of said fairing support.
 16. The fairing of claim 14, wherein said sail track is attached to said front wall of said fairing support.
 17. The fairing of claim 16 wherein said fairing support is a first fairing support, and further comprising: a second of said fairing support positioned between said central segment, said left-side trailing edge, and said right-side trailing edge; a first fairing plate attached to said first side plate of said fairing support and said first side plate of said second fairing support; and a second fairing plate attached to said second side plate of said fairing support and said second side plate of said second fairing support.
 18. The fairing of claim 17, further comprising a roller furler attached to said faring support.
 19. The fairing of claim 14, wherein said sail track is configured to carry a plurality of sail cars configured to be coupled to a sail luff.
 20. The fairing of claim 14, wherein said sail track is configured to receive a bolt rope on a sail luff. 